1. Field of Invention
The invention relates to the field of visual displays. More particularly, the invention relates to the production of balls used in a gyricon or twisting ball visual display and to the production of gyricon balls having sequestered magnetic pads.
2. Description of Related Art
Paper has traditionally been a preferred medium for the presentation and display of text and images. Paper has several characteristics that make it a desirable display medium, including the fact that it is lightweight, thin, portable, flexible, foldable, high-contrast, low-cost, relatively permanent, and readily configured into a myriad of shapes. It can maintain its displayed images without using any electricity. Paper can also be read in ambient light and can be written or marked upon with a pen, pencil, paintbrush, or any number of other implements, including a computer printer.
Unfortunately, paper is not well suited for real-time display purposes. Real-time imagery from computer, video, or other sources cannot be displayed directly with paper, but must be displayed by other means, such as by a cathode-ray tube (CRT) display or a liquid-crystal display (LCD). However, real-time display media lack many of the desirable qualities of paper, such as physical flexibility and stable retention of the displayed image in the absence of an electric power source.
Electric paper combines the desirable qualities of paper with those of real-time display media. Like ordinary paper, electric paper can be written and erased, can be read in ambient light and can retain imposed information in the absence of an electric field or other external retaining force. Also like ordinary paper, electric paper can be made in the form of a light-weight, flexible, durable sheet that can be folded or rolled into a tubular form about any axis and placed into a shirt or coat pocket, and then later retrieved, re-straightened, and read without loss of information. Yet unlike ordinary paper, electric paper can be used to display full-motion and other real-time imagery as well as still images and text. Thus, electric paper can be used in a computer system display screen or a television.
The gyricon, also called the twisting-ball display, rotary ball display, particle display, dipolar particle light valve, etc., provides a technology for making electric paper. A gyricon display is a display that can be altered or addressed. A gyricon display is made up of a multiplicity of optically anisotropic balls which can be selectively rotated to present a desired surface to an observer.
The optical anisotropy of the gyricon balls is provided by dividing the surface of each gyricon ball into two portions. One portion of the surface of each gyricon ball has a first light reflectance or color. The other portion of the surface of the gyricon ball has a different color or a different light reflectance. For example, a gyricon ball can have two distinct hemispheres, one black and the other white. Additionally, each hemisphere can have a distinct electrical characteristic with respect to a dielectric fluid. Accordingly, the gyricon balls are electrically as well as optically anisotropic. The black-and-white gyricon balls are embedded in a sheet of optically transparent material, such as an elastomer layer, that contains a multiplicity of spheroidal cavities. Each of the spheroidal cavities is permeated by a transparent dielectric fluid, such as a plasticizer. The fluid-filled cavities accommodate the gyricon balls, one gyricon ball per cavity, to prevent the balls from migrating within the sheet. Each cavity is slightly larger than the size of the gyricon ball so that each gyricon ball can rotate or move slightly within its cavity.
A gyricon ball can be selectively rotated within its respective fluid-filled cavity by applying an electric field, so that either the black or white hemisphere of the gyricon ball is exposed to an observer viewing the surface of the sheet. By applying an electric field in two dimensions, for example, using a matrix addressing scheme, the black and white sides of the balls can be caused to appear as the image elements, e.g., pixels or subpixels, of a displayed image.
The various exemplary embodiments of the systems and methods of this invention are directed to addressing gyricon displays in which magnetic materials are added to the composition of the gyricon balls and magnetic fields are used to augment the usual electrical addressing fields.
The various exemplary embodiments of the systems and methods of this invention are directed to making gyricon balls with magnetic pads that allows them to be located into two different positions by means of a further stationary magnetic pad. This allows creation of a strong, engineered threshold for gyricon ball rotation, rather than depending upon the naturally occurring threshold.
The various exemplary embodiments of the systems and methods of this invention are directed to sequestering, i.e., hiding, the magnetic pads from sight so they do not decrement the brightness of the display.
The various exemplary embodiments of the systems and methods of this invention are further directed to controlling the engulfing of one hemisphere of a bichromal ball by the other hemisphere of the bichromal ball during the fabrication of the bichromal ball.
In the various exemplary embodiments of the systems and methods of this invention, the magnetic pads, which may be dark in color and which may subtend a substantial part of the visible portion of the white side of the gyricon ball, are sequestered.
In the various exemplary embodiments of the systems and methods of this invention, the gyricon balls are made from a polyethylene plastic, wherein the white sides of the balls are made from this plastic, with titanium dioxide dispersed within, and the black sides of the balls are made from this same plastic, with a black pigment, as well as a chemical called a charging agent, dispersed in within.
In the various exemplary embodiments of the systems and methods of this invention, the magnetic pads are made by dispersing magnetic pigments into the polyethylene plastic.
In the various exemplary embodiments of the systems and methods of this invention, the magnetic pads on the white sides of the gyricon balls are sequestered.
In the various exemplary embodiments of the systems and methods of this invention, the addition of aluminum octoate to either the white side of the gyricon ball or the black side of the gyricon ball causes the pigmented plastic on that side of the ball to attempt to envelope the pigmented plastic on parts of the ball that do not have aluminum octoate added during the ball making process.
In the various exemplary embodiments of the systems and methods of this invention, adding aluminum octoate to the white pigmented plastic causes the magnetic pads on the white sides of the gyricon balls to be enveloped during the ball making process.
In the various exemplary embodiments of the systems and methods of this invention, adding aluminum octoate to the pigmented plastic used to make a first hemisphere of a bichromal ball substantially reduces the likelihood that the pigmented plastic from the second hemisphere of the ball will envelop the first hemisphere, enabling combinations of pigments to be used in the fabrication of bichromal balls that otherwise would undergo engulfing.